U.S. Pat. No. 2,572,571 discloses tris(.beta.-naphthyl)phosphite as a stabilizer to prevent the discoloration of vinyl chloride polymers caused by heat. It has also been suggested as a stabilizer, with .beta.-naphthol, for polyamides. However, tris(.beta.-naphthyl)phosphite has not been found to be satisfactory as a heat or U.V. stabilizer for hydrocarbon polymers, i.e., polymers of butadiene-1,3, isoprene and olefins such as poly(propylene) and (butylene). Tris(.beta.-naphthyl)phosphite is also subject to hydrolysis. A phosphite stabilizer that is more effective as a stabilizer for hydrocarbon and other polymers and is less susceptible to hydrolysis is desired.